Multiband television antenna with multiband parasites



Oct. 4, 1966 c. c. Y. LIU 3,277,491

MULTIBAND TELEVISION ANTENNA WITH MULTIBAND PARASITEs Filed Oct. 11, 1963 :3 Sheets-Sheet 1 55b is 56d 56b 2 57 d 57:; 58d 1 59d 59b 59 ifnll i? Mil INVENTOR. CHARLES C. Y. LIU

ATTORNEYS Oct. 4, 1966 c. (3. Y. LIU 3,277,491

MULTIBAND TELEVISION ANTENNA WITH MULTIBAND PARASITES Filed Oct. 11, 1963 5 Sheets-Sheet 2 INVENTOR, CHARLES C.Y. LlU

BY ga 59 qna alg ATTORNEYS C. C. Y. LIU

Oct. 4, 1966 MULTIBAND TELEVISION ANTENNA WITH MULTIBAND PARASITES 5 Sheets-Sheet 5 Filed Oct. 11 1965 ozw30wmu SE 6 B04 INVENTOR.

m L w e 8 s Y E N m H A United States Patent MULTIBAND TELEVISION ANTENNA WITH MULTHEAND PARASITES Charles C. Y. Lin, Ellenville, N.Y., assignor to Channel Master Corporation, Ellenville, N.Y., a corporation of New York Filed Oct. 11, 1963, Ser. No. 315,524 12 Claims. (Cl. 343-802) The present invention relates to antennas for the propagation or reception of electromagnetic energy of radio frequencies and more particularly to such antennas adapted for use in noncontiguous frequency bands such as the high band and the low band portions of the frequencies allocated to VHF television (and preferably also the FM radio band which adjoins the low band), or in very wide frequency bands, where the ratio of the highest frequency to the lowest frequency be 3 or more.

This invention represents in part an improvement of the antenna disclosed in United Stat-es Patent 3,086,206 for End Fire Planar Dipole Array With Line Transposition Between Dipoles and Impedance Increase Toward Feed, issued April 16, 1963, to Harry Greenberg.

The wide-spread use of television receivers has brought about a demand for highly developed television receiving antennas, particularly for use in areas far removed from transmitters from which it is desired to receive television broadcasts. Antennas for these remote areas are customarily called fringe-area antennas. A prime requisite for such an antenna is that it have a high degree of signal gathering ability. This ability is commonly referred to in terms of gain, gain being defined as the antennas signal-gathering ability compared to a standard dipole antenna, and usually expressed in decibels (db). Another important requisite is that the antenna be able to discriminate against broadcasts from other than desired directions. This requires that the receptivity pattern have essentially a single major lobe or at most two oppositely directed lobes, of as much sharpness as is practicable or desirable for particular situations.

Antennas are inherently frequency selective devices which respond best to a limited range of frequencies and are substantially ineffective outside of this range. While one could provide a separate television antenna for each television channel to be received, this would obviously be impractical. It is, of course, most desirable to have a single antenna for all television channels. Such an antenna is customarily known as an all-channel antenna. The manner in which television frequencies in the VHF television band have been allocated has rendered it most difficult to provide an efficient all-channel VHF television antenna.

While there are only twelve VHF television channels, each six megacycles wide, these channels are not allocated to wholly contiguous frequency ranges, but are divided into a low band extending from 54 megacycles to 88 megacycles and a high band extending from 174 megacycles to 216 megacycles. Thus the highest VHF television frequency of 216 megacycles exceeds the lowest VHF television frequency of 54 megacycles by a factor of four. This band-width has heretofore rendered exceedingly difiicult the design of a single all-channel antenna.

By the present invention a television antenna for all VHF television channels is provided which is of remarkable efiiciency. This is accomplished by providing a multiband array of active elements such as a front-fed, in-line array with a multiplicity of parasitic director elements which complete array effectively covers both the low band portion and the high band portion of the VHF television range.

In accordance with the invention, there is added to 'ice the array of active elements, which may be conventional, a director array of one or more parasites of novel form. It is known, of course, that the gain and directivity of antenna arrays can in many cases be enhanced by the addition of parasitic directors. Previously, however, such parasitic directors were of limited utility for multiband antennas, due to the fact that parasite configurations were not available which would be effective throughout widely spaced frequency bands, such as the low VI-LF television band and the high VHF television band. It has therefore frequently been a common practice to provide separate parasitic elements for the low band and the high band. But this has also been less than completely satisfactory because of the increased number of parasites re quired and the inability to completely eliminate deleterious effects of low band parasites during high band operation and vice versa.

The present invention provides a parasite configuration useful for an element or elements of a director array which provides a substantial contribution in gain and directivity throughout the low VHF television band, the high VHF television band and also the FM radio band (which is adjacent to and slightly higher in frequency than the low VHF television band). The use of such parasites in connection with a multiband array of active antenna elements makes it possible to provide increased gain and directivity with a minimum number of additional parasitic elements, and with virtually no compromise between low band and high band operation of the entire television array.

A complete antenna array according to the invention provides an exceptionally good directivity characteristic and front-to-back-ratio. This ratio is a measure of the ability of the antenna to reject signals from directions opposite to those of the desired signal. This is a particularly important consideration at the present time in fringe areas due to the increased number of television transmitters, and due to the fact that, in fringe areas, transmitters within the range of a particular receiver will usually be located in several different directions. Thus a high degree of directivity and a high front-to-baokratio is very desirable for eliminating both co-channel and adjacent channel interference. The high front-toback-ratio of antennas according to the present invention is provided in a substantial part by the characteristics of the parasitic director section of the antenna.

It should be noted that the parasitic directors of the present invention may be used with various other forms of dualband or mutiband active element array, for example arraysof the type of United States Patent No. 2,817,085, issued December 17, 1957, to Jerome Schwartz and Yuem Tze Lo.

In addition to providing the advantages and features described above, it is an object of the present invention to provide a high-gain television antenna having active and parastic director elements, which antenna is effective on two separated frequency bands, and particularly where such two bands bear approximately a harmonic relationship.

It is another object of the invention to provide parasitic elements for a television or other antenna in which, each such parasitic element operates at a low frequency within the antenna operating frequency range as an efiicient single half-wave parasite and at a high frequency within the antenna operating frequency range as two eflicient substantially colinear half-Wave parasitic elements.

It is yet another object of the present invention to provide such a television antenna having several in-line active dipole elements fed from the front of the array by a transmission line, wherein the transmission line connecting the antenna elements has a transposition between each antenna element and its succeeding element.

It is a further object of the present invention to provide a television antenna of the foregoing type wherein the antenna elements are caused to have a good reception pattern or directivity by use of a relatively short parasitic element closely spaced in front of each simple active dipole element.

Other objects and advantages of the present invention will be apparent from a consideration of the following description in conjunction with the appended drawings, in which:

FIGURE 1 is a perspective view of an antenna array according to the present invention;

FIGURE 2 is a plan view of the antenna array of FIG- URE 1;

FIGURE 3 is an elevational View of the antenna of FIGURES l and 2 taken along the line 33 in FIGURE FIGURE 4 is a schematic diagram of the parasite of FIGURE 3 indicating its operation at low frequencies;

FIGURE 5 is a schematic diagram of the parasite of FIGURE 3 indicating its operation at high frequencies;

FIGURE 6 is a schematic diagram of the parasite of FIGURE 3 indicating its current distribution at low frequencies; and

FIGURE 7 is a schematic diagram of the parasite of FIGURE 3 indicating its current distribution at high frequencies.

Throughout this discussion, the antenna arrays according to the present invention may be considered from time to time as transmitting antennas. This is a technique often employed in the antenna art, and by the principle of reciprocity for transmitting and receiving antennas, conclusions reached by considering the antenna as a transmitting antenna are also known to be applicable for the antenna utilized as a receiving antenna. Obviously, antennas according to the present invention may be utilized either as transmitting antennas or as receiving antennas, but are primarily designed for use as television receiving antennas.

Referring now to FIGURES 1 to 3, the antenna array 44 has a supporting mast 46 and a horizontal boom 48. A signal transmission line 50 is provided to connect the antenna array to a utilization device such as a television receiver.

The array 44 has nine active elements 51 to 59 of progressively varying length, each comprising substantially co-linear arms 51a and 5112 through 59a and 59b, inclusive. The active elements 51 to 59 are interconnected by an interconnecting transmission line harness 60 in a fashion shown in FIGURES l and 2. Insulating supports 51c to 59c are provided for securing the arms of the antenna elements in insulated relation to the boom 48 and to each other. Each of the dipoles 51 to 59 is provided with a respective close-spaced short parasitic element 51d to 59d, on the front side of the dipole.

The short parasitic elements 51d to 59d do not substantially affect the operation of the dipoles 51 to 59 on the low-band frequencies; hence the lengths of the dipole arms can be selected as appropriate for low-band operation, and to the extent that the operation is affected compensation can be made by slightly altering the lengths of the dipole arms. The parasitic elements 51d to 59d are effective at high-band frequencies to provide a sharp directivity pattern for the active elements and hence for the array of active elements as a whole. In addition the length of each parasitic element 51d to 59d and its spacing from its respective dipole can be individually selected in order that the impedance of the dipole-parasite combination on the high-band can be determined substantially independently of the dipole impedance at low-band frequencies. Thus the close-spaced parasites of the antenna of FIGURES 1 and 2 providean independent parameter for determination of impedance at highband frequencies.

The operation of the active elements of the antenna shown is dependent upon impedance relations of the ele- 4 ments, the transposed transmission line arrangement, and other features, all as set forth in the US. Patent 3,086,206, and the detailed theory of operation of the active element section of the antenna will not be repeated here.

The present invention is of course not limited to use with the forms of active elements shown with respect to the above described antenna. Other types of dual-band or multiband active element sections may be employed.

According to the invention, the antenna array 44 is provided with parasitic director elements 61 to 68 inclusive which are of novel form. The details of the structure of the parasitic director elements 61 to 68 may best be understood by reference to FIGURE 3, which is an elevational view of a representative parasitic director element 64. In the antenna illustrated in FIGURES 1-3, each of the parasitic elements 61 to 68 is identical in construction. It is a desirable feature of the parasitic director construction that a director array of many parasitic elements of identical construction will operate in an eflicient manner. Obviously, it is advantageous from the point of view of economy and facility of construction to utilize identical components wherever possible. However, if for any reason it may be desired, the parasitic elements of a particular array may be of respectively different size or length, for example of graduated length with the shorter elements toward the front of the antenna.

The parasitic director element 64 comprises two conductive arms 64a and 64b which may be formed for example of aluminum tubing. The arms 64a and 6411 are connected by a non-conductive mounting unit of plastic resin or other suitable material to the horizontal boom 48.

As is customary in the art, the arms 64a and 641) are preferably pivotally mounted to mounting unit 640, so that they may be folded for convenience in shipping and shaped into place prior to installment of the antenna. The construction by which the antenna is folded for shipping forms no part of the present invention, however, and is not indicated in detail.

Mounted on arm 64a of parasite 64 are a pair of elongated conductive members 64 and 64g, arranged at an acute angle to the arm 64a with the outer end of each of the elongated conductive members 64 and 64g conductively and physically connected to the arm 64a intermediate the ends thereof. For convenience the elongated conductive members 64 and 64g will be referred to as whiskers 64) and 64g. In the specific embodiment of the parasite 64 illustrated in FIGURE 3 the junction of the whiskers 64] and 64g with the parasite arm 64a is between the center of the arm 64a and its outer end but the invention is not necessarily limited to this situation.

The arms 64 and 64g are preferably also pivotally mounted with respect to the arm 64a as by a mounting bracket 64:, so that the wiskers 64] and 64g may also be compactly folded for shipment. The details of the folding and detent arrangement for arms 64;! and 64g has not been shown and described in detail as it does not form an essential part of the present invention. Parasitic arm 64b is of course provided with whiskers 64d and 74e together with mounting bracket 64h, all similar to their counterparts previously described with relation to parasite arm For reasons which will later be more fully explained, the inner ends of arms 64a and 6412 represented by pivots 64j and 64k respectively are insulated from each other and spaced by a predetermined amount from each other and from the conductive boom 48 to provide a predetermined electric capacitance between the inner ends of arms 64a and 6411, which arms it will be noted are otherwise not conductively connected. Obviously, a capacitor should be connected between the inner ends of arms 64a and 64b to provide a desired capacitive coupling rather than to rely on the electrical capacitance inherent in the physical structure.

The provision whereby arms 64a and 6421 are not conductively connected attheir inner ends but are rather coupled by a capacitance serves to provide electrical characteristics for the parasite 64 which make it effective throughout the frequency range of interest, in the illustrated case, the low VHF television band, the FM radio band and the high VHF television band. In theory the desirable electrical characteristics could be obtained by changing the physical characteristics of the parasite structure, but in practice this is found to be impractical for various reasons, such as for the reason that alterations tending to provide the desired electrical characteristics also create undesired proximity or overlap of the inner ends of whiskers 64d, 64e, 64 and 64g.

It should particularly be noted that Whiskers 64d, 64e, 64 and 64g are of unusual form in that they comprise an elongated loop of conductive rod. The whiskers may be formed from aluminum rod, for example, by forming the conductive whiskers as a loop, they are given effectively a fat electrical cross-section which has been found to be highly desirable in obtaining efficient operation of the parasite throughout the wide range of frequencies of interest. Other known expedients could be utilized to provide whiskers which are of large effective electrical cross-section but the conductive loop form i1- lustrated is particularly desirable in that it is economical of material and provides a simple structure.

The operation of the parasites such as shown in FIG- URE 3, as it is presently understood, will be explained with reference to FIGURES 4 through 7. FIGURE 4 is a schematic diagram useful in understanding the operation of the parasite at low frequency, for example the low VHF television band. The various elements in FIGURE 4 are given the same reference numerals as in FIGURE 3; the capacitive coupling between inner ends of arms 64a and 64b is schematically represented by a capacitor 64m. In FIGURE 4 the portions of the parasite which are effective at low frequencies are shown in solid lines and those portions which are substantially ineflfective are shown in dashed lines.

Whiskers 64d, 642, 64] and 64g shown in dashed lines are relatively ineffective at the low frequencies because they each represent a stub which has a length in terms of wavelengths of the low frequency, such that the current distribution in the parasite is almost as if the whiskers were not present.

FIGURE 5 is a schematic representation for signals of high frequency, in which case the whiskers are of a length in terms of wavelengths of the high frequency (somewhat greater than one-quarter wavelength) such that their presence materially affects the current distribution. On the other hand, in the high frequency case the portion of arms 64a and 64b which is inward of the junction between the whiskers and the arms 64a and 64b is substantially ineffective because the aforesaid junction represents approximately a voltage null point for high frequency operation. It should be mentioned at this point that the function of the capacitance indicated at 64m is to allow the physical length of arm 64 to be increased to avoid physical or electrical interference between the ends of whiskers 64d and 64 or between the ends of whiskers 64a and 64g, at the same time retaining the effect electrically of shorter arms. This should be contrasted with previous dual band parasites which employ an inductance between the inner ends of the parasite arms. Such an inductance serves to provide an electrical connection of low impedance between the arms at low frequencies and an isolation of high impedance between the arms at high frequencies. Thus the inductance arrangement seeks to provide a broadly similar effect to that provided by the present arrangement, but it is based on a distinctly different theory and has a different structure.

FIGURES 6 and 7 show respectively the current distributions for the parasite at low and high frequencies and bring out the fact that the parasite operates as a single half-wave element at low [frequency and that it operates as a pair of approximately colinear half-wave ele- 6 ments at high frequency, as also indicated by FIGURES 4 and 5.

The function of the parasitic element of FIGURE 3 has been described as if it were the only parasite in the antenna array, which in some cases it could be. It is, however, known that multiple parasitic directors may be utilized advantageously after the fashion of a yagi antenna to approve improved gain and directiw'ty. The parasitic element of FIGURE 3 is susceptible of being used in considerable number in a director array as illustrated in FIGURES 1 and 2. Parasitic directors of the type shown in FIGURE 3 can be added at least up to eight in number with incremental improvement in antenna characteristics for each added parasitic director. of course, the improvement contributed by the eighth parasite is not as great as that contributed by the first. It will be appreciated that according to the characteristics desired any number from one to eight or more parasites as in FIGURE 3 may be incorporated in an antenna array.

While parasites according to the present invention have been described and illustrated for director elements, they are also susceptible of use as reflector elements.

As an illustration of a specific embodiment of the antenna, the dimensions of a representative antenna shown in FIGURES 1 to 3 are presented hereinbelow in tabular form.

Table 1 Elem. No. Length, in. Spacing from Bear Adjac. Elem., in.

64rl,e,f and g. 19 61 through 67 G2 12 68 62 9 24% 3 52 9 25%, 3 60% 9 26 3 64% 8% Active element diameter%".

Active element termina1s-3-inch spacing. Harness wire-W diameter.

Whisker wire-$4" diameter.

Whisker l0op1% across.

It will be understood that the foregoing illustrations of a specific antenna is presented by way of example only and are not intended to be limiting. Numerous variations in the actual construction of the antenna will be apparent to those of skill in the art. For example, active element arrays of types dilferent than those illustrated may be utilized. However, it is preferred that the active elements be of the type which operate in higher order modes in at least part of the frequency range. It is also somewhat to be preferred that the active elements be of the type which operate in a higher order mode in such a manner as to have greater signal gathering ability than the standard half-wave dipole, that is, that they operate as a longer-than-half-wave dipole or as a set of colinear half-wave dipoles, so as to have positive. gain. This enhances the high-band efiiciency of the antenna array disclosed in FIGURES l to 3.

While the present invention has been specifically described with respect -to VHF television and FM radio broadcasting, the principles of the invention are useful whenever extremely wide frequency ranges are involved of the order of 3 to 1 or more, and is not limited to harmonically related frequency bands.

Numerous other Variations will be apparent to those of skill in the art in addition to those described or suggested and it is accordingly desired that the scope of the invention not be restricted to those embodiments shown or suggested but that it shall be limited solely by the scope of the appended claims.

Certain theories of operation of antennas according to the present invention have been set forth which are believed to be correct, but the scope of the invention is in no way intended to be limited by the theory of operation described, and the operability of the antenna is based upon performane of the actual embodiment presented 'by way of example and not upon theoretical considerations.

What is claimed is:

1. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms in a common horizontal plane with and spaced from said active dipole element, each said parasitic element arm being capacitively coupled at its inner end to the inner end of the other arm of said parasitic element, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter Wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at .a portion of said arm intermediate the ends thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

2. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms substantially parallel to, in a common horizontal plane with and sequentially spaced in front of the front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a portion of said arm intermediate the ends thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

3. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including a plurality of active horizontal dipole antenna elements, and a plurality of identical parasitic elements, each having oppositely extending elongated conductive arms substantially parallel to, in a common horizontal plane with and sequentially spaced in front ofthe front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section being joined con-ductively with its respective arm at a portion of said arm intermediate the ends thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

4. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least tWo-to-one comprising an active section operative over said frequency range including a plurality of active horizontal dipole antenna elements, and a plurality of identical parasitic elements, each having oppositely extending elongated conductive arms substantially parallel to, in a comm-on horizontal Plane with and sequentially spaced in front of the front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wavelength of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a portion of said arm intermediate the ends thereof and extending at an angle of approximately 20 with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

5. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms in a common horizontal plane with and spaced from said active dipole element, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a portion of said arm intermediate the ends thereof and extending at an angle of approximately 20 with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

6. In an antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one, a parasitic director element having oppositely extending elongated conductive arms, each said parasitic element arm being capacitively coupled at its inner end to the inner end of the other arm of said parasitic element, each said arm having one upwardly extending and one downwardly extending conductive branch section comprising an elongated wire loop, each said conductive branch section being joined conductively with its respective arm at a portion of said arm intermediate the ends thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

7. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms in a common horizontal plane with and spaced from said active dipole element, each said parasitic element arm being capacitively coupled at its inner end to the inner end of the other arm of said parasitic element, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form :a low frequency parasitic element and said branch sections forming high band parasitic elements.

8. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms substantially parallel to, in a common horizontal plane with and sequentially spaced in front of the front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band par-asitic elements.

9. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including a plurality of active horizontal dipole antenna elements, and a plurality of identical parasitic elements, each having oppositely extending elongated conductive arms substantially parallel to, in a common horizontal plane with and sequentially spaced in front of the front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

10. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including a plurality of active horizontal dipole antenna elements, and a plurality of identical parasitic elements, each having oppositely extending elongated conductive arms substantially parallel to, in a common horizontal plane with and sequentially spaced in front of the front one of said active dipole elements, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wavelength of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an angle of approximately 20 with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

11. An antenna array for operation over a frequency range including widely separated frequencies bearing a ratio of at least two-to-one comprising an active section operative over said frequency range including at least one active horizontal dipole antenna element, and at least one parasitic element having oppositely extending elongated conductive arms in a common horizontal plane with and spaced from said active dipole element, each said parasitic element arm having its inner end spaced from the inner end of the other arm of said parasitic element to provide capacitive coupling therebetween, each said arm having one upwardly extending and one downwardly extending conductive branch section, each said conductive branch section comprising an elongated wire loop having a minimum transverse dimension which is small compared to a quarter wave-length of the highest antenna frequency and large relative to the wire diameter, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an angle of approximately 20 with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

12. In an antenna array for operation over a frequency range including widely separated frequencies hearing a ratio of at least two-to-one, a parasitic director element having oppositely extending elongated conductive arms, each said parasitic element arm being capacitively coupled at its inner end to the inner end of the other arm of said parasitic element, each said arm having one upwardly extending and one downwardly extending conductive branch section comprising an elongated wire loop, each said conductive branch section being joined conductively with its respective arm at a point substantially displaced from the midpoint of said arm toward the outer end thereof and extending at an acute angle with the inner portion of said arm, each said branch section terminating short of the vertical projection of the inner end of its respective arm, said arms cooperating with said branch sections to form a low frequency parasitic element and said branch sections forming high band parasitic elements.

References Cited by the Examiner UNITED STATES PATENTS 2,648,768 8/ 1953 Woodward 343792 2,980,912 4/ 1961 Anderson 343802 3,086,206 4/1963 Greenberg 343815- 3,092,835 6/1963 Jaytanie 3438 17 X A. R. MORGANSTERN, M. NUSSBAUM,

Assistant Examiners. 

12. IN AN ANTENNA ARRAY FOR OPERATION OVER A FREQUENCY RANGE INCLUDING WIDELY SEPARATED FREQUENCIES BEARING RATIO OF AT LEAST TWO-TO-ONE, A PARASITIC DIRECTOR ELEMENT HAVING OPPOSITELY EXTENDING ELONGATED CONDUCTIVE ARMS, EACH SAID PARASITIC ELEMENT ARM BEING CAPACITIVELY COUPLED AT ITS INNER END TO THE INNER END OF THE OTHER ARM OF SAID PARASITIC ELEMENT, EACH SAID ARM HAVING ONE UPWARDLY EXTENDING AND ONE DOWNWARDLY EXTENDING CONDUCTIVE BRANCH SECTION COMPRISING AN ELONGATED WIRE LOOP, EACH SAID CONDUCTIVE BRANCH SECTION BEING JOINED CONDUCTIVELY WITH ITS RESPECTIVE ARM AT A POINT SUBSTANTIALLY DISPLACED FROM THE MIDPOINT OF SAID ARM TOWARD THE OUTER END THEREOF AND EXTENDING AT AN ACUTE ANGLE WITH THE INNER PORTION OF SAID ARM, EACH SAID BRANCH SECTION TERMINATING SHORT OF THE VERTICAL PROJECTION OF THE INNER END OF ITS RESPECTIE ARM, SAID ARMS COOPERATING WITH SAID BRANCH SECTIONS TO FROM A LOW FREQUENCY PARASITIC ELEMENT AND SAID BRANCH SECTIONS FORMING HIGH BAND PARASITIC ELEMENTS. 